A tangential impact wrench periodically, briefly provides a large tightening torque for tightening screw connections or for placing screw anchors. A continuous lesser torque is output at a handle or a holder of the tangential impact wrench, which the user or a stand must counteract.
The tangential impact wrench is suitable for putting screws into manifold materials of varying hardness, for example, into stone, concrete, brick, limestone, and cellular concrete. Screws are typically inserted far enough that the screw head rests on a substrate (workpiece). The screw may not be tightened further, because this results in damage to the screw or the substrate. For example, the screw head may be twisted off, a round hole may be cut into the substrate by the screw thread, or the substrate may be stripped out by the screw thread.
EP 1 510 394 B1 describes an automated shutdown of an impact wrench. The impact wrench monitors the applied tightening torque. If the tightening torque exceeds a threshold value to be set, a primary drive of the impact wrench is shut down.
W0 2007/015661 A2 describes an automated shutdown of an impact wrench, in that a rotational angle of the screw is measured for each impact. If the rotational angle falls below a threshold value, the screw is considered tightened and the impact wrench is shut down.
DE 195 03 524 A1 describes a control method, in which an initial output torque is kept lower than a required torque in order to prevent overtightening of a screw. The torque is subsequently increased step-by-step in an iterative sequence.
EP 1 695 794 A2 describes an estimation unit, which estimates a torque transmitted to a screw.
The known methods require an establishment of a threshold value, which is either permanently predefined or is to be set by a manual worker. In both cases, the risk arises that the threshold value is set inappropriately for a substrate (workpiece).